Few days back I have installed ecryptfs, created a private directory using it. Now my Ubuntu login became super slow. I have tried removing ecryptfs from Synaptic. I found It, it can not be deleted that way. Somewhere I have read about this command

ecryptfs-setup-private --undo

But this command displays a rather confusing list of commands on terminal. I don't want to mess up my installation, neither want to loose my administrator account.

Now my question is, how can I safely remove /home/user/Private (.Private) and remove ecryptfs encryption ?

This command populates the $PRIVATE variable with the path to your private directory. Either the path is stored in ~/.ecryptfs/Private.mnt file (where ~ is your home directory) or if the file doesn't exist, it will fall back to ~/Private path.
You can then run echo $PRIVATE command to verify content of the PRIVATE variable.
When you see $PRIVATE in the following commands, it will be substituted with the contents of the variable, ~/Private in your case.

Ensure that you have moved all relevant data out of your $PRIVATE directory

This is important.

Unmount your encrypted private directory

$ ecryptfs-umount-private

eCryptFS is kind of a filesystem which is mounted in user space (Wikipedia explains what's mounting about. That's also the reason why the Private folder cannot be removed so easily. Think of it as kind of proxy which transparently encrypts and decrypts your files. This command un-mounts the folder which effectively disables the encryption.

Make your Private directory writable again

$ chmod 700 $PRIVATE

chmod sets file permissions. In this case, you say: "make file/directory stored in $PRIVATE readable, writable and executable for me (700)" – you can't otherwise delete the directory since you don't have write access.

Dont just copy the commands from Terminal. Please post explanations of those commands,how I use them, what cautious measurements should I take etc.
–
Curious ApprenticeMay 4 '12 at 17:55

I see you are really curious. :) I have added explanation what those commands do, feel free to ask if anything is unclear. Given you have use standard configuration, you shouldn't run into any problems.
–
jnvMay 4 '12 at 18:31

Ohh yes ! I am Curious :D. And Thank you for trying to clear things up. Ok now you have allowed me to ask further questions, so here is what I need to know more: Why I need to use a $Private variable ? How I run the command ? I have tried copy pasting it ($ PRIVATE=cat ~/.ecryptfs/Private.mnt 2>/dev/null || echo $HOME/Private) and It outputted "$ Command Not Found !"
–
Curious ApprenticeMay 5 '12 at 17:02

Next thing is, why I need to make $Private writable ? Is it the variable which holds the path or it is the Folder itself ? I knew how to see hidden folders, and Private directory is automatically mounted at my Login. When Im trying to remove ecryptfs and that lib file it shows an error which states that "Device is busy".
–
Curious ApprenticeMay 5 '12 at 17:06